Concrete slab key joint forming strip



Nov. 29, 1966 .0. GAETKE 3,288,042

CONCRETE SLAB KEY JOINT FORMING STRIP Filed April 17, 1964 I I INVENTOR. I J GEORGE 0. GAETKE BY ATTORNEY United States Patent Ofiice 3 ,288,042 late'nted Nov. 29, 1966 CONCRETE SLAB K-EY JOINT FORMING STRIP George 0. Gaetke, San Francisco, Calif., assignor to Burke Concrete Accessories, Inc., a corporation of California Filed Apr. 17, 1964, Ser. No. 360,699 The portion of the term of the patent subsequent to Aug. 11, 1981, has been dedicated to the Public Claims. (Cl. 94-51) This invention relates to the construction of concrete slabs and more particularly to a key joint forming strip utilized in the construction of concrete slabs of roadways, fioors and air fields.

This invention is a continuation-in-part of my pending patent application entitled Concrete Slab Key Joint Forming Strip, Serial No. 240,272, filed November 22, 1962, now Patent No. 3,143,783.

The present invention provides an improved sheet metal divider strip adapted to form a key joint between two adjacent concrete slabs, permitting the expansion and contraction of the slabs with changes in temperature while at the same time preventing the vertical displacement of such slabs with respect to each other. The divider strip embodying this invention is adapted to be suspended on suitably placed vertical stakes driven into the ground or sub-grade and arranged with their upper ends well below grade level. The upper ends of the stakes are provided with apertures which are adapted to receive offset protuberances formed in the strip by a suitable crimping tool, to prevent the displacement of the strip on the stakes. The upper edge of the strip is formed with a longitudinal, inverted substantially Y-shaped portion which provides a channel-shaped recess or socket within which the upper ends of the stakes are adapted to fit to support the strip in a vertical position with the upper edge thereof at grade level.

The primary object of the present invention is to provide a key joint forming divider strip employed in the construction of concrete roadways, floors and air field runways, which is formed at its upper edge with a longitudinal, inverted substantially Y-shaped portion having an inverted L-shaped flange defining a channel-shaped recess positioned well below the upper narrow straight edge of the strip for supporting the strip on a number of metal stakes driven into the prepared sub-grade, to be vertically positioned so concrete may be poured on the sub-grade, first at one side of the strip to form a concrete slab and then at the other side thereof to form an adjoining slab, thereby covering the inverted L-shaped flange and leaving the upper narrow edge of the strip exposed so it may be used as a leveling rod support in smoothing the upper faces of the slabs and subsequently to provide a rectilinear marker.

Other and further objects of my invention will be pointed out hereinafter or will be indicated in the appended claims or will be obvious to one skilled in the art upon an understanding of the present disclosure. For the purposeof this application, I have elected to show herein certain forms and details of a combination divider strip and supporting means therefor, which is representative of my invention; it is to be understood, however, that the embodiment of 'my invention herein shown and described is for purposes of illustration only, and that therefore it is not to be regarded as exhaustive of the variations of the invention in the art.

In the accompanying drawing:

FIG. 1 is a vertical sectional view taken through adjoining concrete slabs, showing the metal divider strip comprising the present invention positioned there'between;

FIG. 2 is a perspective view showing, a portion of a metal divider strip supported on a stake;

FIG. 3 is a diagrammatic view, partly in section, showing a crimping tool bending the flange member of the strip to provide an offset protuberance extending into the aperture in the upper portion of a supporting stake; and

FIG. 4 is an enlarged perspective view of a supporting stake for the divider strip; and

FIG. 5 is a perspective view of the crimping tool used to form an offset protuberance in the flange member of the strip.

Referring to the drawing, the numeral 1 designates a key joint forming strip embodying the principles of the present invention, made preferably from sheet metal such as steel or aluminum. The strip comprises a lower planar portion or member 2, an upper coplanar portion or member 3, outwardly extending planar portions or members 4, 4 arranged preferably in converging relationship with respect to each other, and an intermediate planar portion or member 5. The lower edge of the lower portion 2 is folded over to provide a reenforcing bead 6 to increase,

the rigidity of the strip. The outwardly converging portions 4, 4 together with the intermediate portion 5 form a longitudinally extending protrusion or key deformation portion ormember of semihexagonal shape, which is adapted to form a tongue and groove joint between the adjacent faces of concrete slabs constructed at opposite sides of the strip. The intermediate portion 5 may be provided with a number of suitably spaced holes 7 adapted to receive metal reenforcing dowels or rods 8 slidably. The upper planar portion 3 is preferably provided with a number of longitudinally spaced preformed tongues 9 which, when the strip is used as a header board, are bent outwardly to provide connecting means between the strip and an adjacent concrete slab for preventing the separation of the slab from the strip when such slab hardens and contacts.

The upper portion of the length 3, in cross-section, is similar to an inverted Y in shape. The length 3 is bent outwardly as at 10 to provide a longitudinal shoulder, and its upper portion connecting with the shoulder is folded over at its upper edge in a direction away from the key' deformation portion to provide a narrow upper straight edge 11 on the strip. The folded over portion of the length 3 extends downwardly against the latter as at 12, then outwardly as at 13 to provide a shoulder substantially horizontally aligned with the shoulder 10, and then downwardly as at 14. The outwardly and downwardly disposed portions 13 and 14 form an inverted L-shaped flange, which in combination with the upper planar portion 3 and the shoulder 10 forms a longitudinal socket 15 of inverted channel-shaped configuration adapted to receive the upper ends of metal stakes 16 (only one of which is shown), the said ends being arranged uniformly below grade level.

The divider strip is adapted to be suspended on and supported bya number of suitably aligned, substantially vertical stakes 16 driven to predetermined depths into the prepared sub-grade or ground upon which the concrete crown of a roadway is to be constructed. The stakes have upper end portions which are adapted to fit in the longitudinal socket 15 slidably. The upper end portions of the stakes are formed with apertures 17 which are positioned in horizontal alignment with the lower edge of the downwardly disposed part 14 of the flange, so that by crimping the said lower edge inwardly by means of a tool 18, an offset protuberance 19 may be formed, which extends into the aperture of a stake to prevent the displacement of the strip.

The shoulders and 13 of the upper length 3 of the strip rest upon the upper ends of the stakes to support the strip in a substantially vertical position with the lower planar portion 2 and the upper planar portion 3 arranged in abutting relation with respect to the aligned stakes. The shoulders 10 and 13 forming the upper side of the socket 15 are positioned substantially below the straight edge 11 of the strip, and since these shoulders rest upon the upper ends of the alignedstakes, the strip will be supported vertically with the upper straight edge positioned well above the said upper ends of the stakes.

The divider strip may vary in width in accordance with the desired thickness of the concrete slabs and 21, but in normal practice the height of the strip should be such that with the lower edge 22 thereof spaced slightly above the prepared sub-grade 23 its upper straight edge 11 will be disposed at the grade level of the upper surfaces of the slabs. Preparatory to the formation of the slabs, a number of stakes 16 will be driven to a suitable depth into the prepared sub-grade or ground along a predetermined line defining the inner edge of the concrete slab 20 so that the supported strip will be disposed with the upper edge 11 thereof arranged at the desired grade level. The strip is thus arranged in a supported position on the stakes with the upper ends of the latter extending into the socket 15 and in engaging relationship with the shoulders 10 and 13. Concrete is poured first onto the subgrade at the side of the strip having the key deformation portion, to form the concrete slab 20 and then at the opposite side of such strip to form the slab 21. The concrete forming the slab 21 fills the area within the key deformation portion of the strip, thereby completing the formation of a tongue and groove type of juncture between the slabs. After the pouring of the concrete forming the slabs 20 and 21, the upper surfaces thereof may be suitably smoothed and leveled by means of a rod or screed supported during its back and forth movement on the upper straight edge 11 of the strip.

It will be noted that the upper ends of the stakes being positioned well below the upper exposed edge 11 of the strip, and being covered by concrete material overlying the shoulders 10 and 13 will continue to be concealed below the upper surfaces of the slabs even though the said upper edge of the strip might be worn down by the continued travel of vehicles over the roadway.

While in certain instances it might be preferable to have the depending flange 14 of a strip formed with a number of offset protuberances 19 extending into the apertures 17 of all or most of the stakes, it is to be noted that one or more strips comprising the form may be held against displacement on the stakes by having but one protuberance formed in the flange 14 of each strip.

What I claim is:

1. A concrete form of the type used in forming a key contraction joint between adjacent concrete slabs, comprising in combination:

(A) a plurality of stakes adapted to be vertically set in transversely aligned relationship with the upper ends thereof disposed uniformly below grade level, said stakes each having at least one recess therein with upper and lower boundaries disposed at predetermined distances beneath the upper end thereof; and,

(B) an eolngated sheet metal strip adapted to be supported on said stakes, said strip having:

( 1) longitudinal upper end lower coplanar members adapted to abut against said stakes upon being supported thereon;

(2) a longitudinal key deform-ation member interplanar member, a longitudinal shoulder fixed.

relative to said member and extending outwardly therefrom, and a longitudinal flange depending.

downwardly from said shoulder by a distance intermediate the predetermined distances at which the upper and lower boundaries of said recess are disposed beneath the upper end of said stake, and wherein:

(a) said channel is adapted to be received over the upper ends of said stakes to support said strip thereon; and,

(b) said flange is adapted to be deformed into the recess of a stake received in said channel to maintain said strip in substantially fixed orientation relative to said stake.

2. A concrete form of the type used in forming a key contraction joint between adjacentconcrete slabs, com prising in combination:

(A) a plurality of stakes adapted to be vertically set in transversely aligned relationship with the upper ends thereof disposed uniformly below grade level; and,

(B) an elongated strip'adapted tobe supported on said stakes, said strip having: 4 I

(1) longitudinal upper and lower substantially coplanar'members adapted to abut against said stake-s upon being supported thereon;

(2) a longitudinal key deformation member inter posed between and connected to the upper and 'lower coplanar members; and,

(3) an inverted socket formed on the upper (50- planar member and adapted to be fecei'vedover said stakes to support said strip thereon, said socket comprising: I

(a) a first portion extending longitudinally of and laterally from the upper edge of the upper of said coplanar mernbers';

(b) a second portion extending longitudinal ly of and substantial vertically from said first portion to define a thin section; and,

(c) a third portion extending from and longi tudina=lly of said second portion in spaced relationship to the upper edge thereof and in spaced substantially opposed relationship to the upper of said coplanar members.

3. A concrete form according to claim 2, wherein:

(A) said second portion comprises:

(1) a first segment extendign longitudinally of and substantially vertically from said first portion; and,

(2) a second segment extending from and longitudinally of said first segment in folded upon relationship with respect thereto; and,

(B) said third portion extends from and longitudinally of said second segment.

4. A concrete form according to claim 2 wherein said second portion is spaced laterally from the upper of said coplanar members.

5. A concrete form according to claim 2, wherein:

(A) said stakes each have at least one recess in the upper portion thereof;

(B) upon receipt of said socket over a stake the third portion of said socket extend-s at least partially over the recess in said stake; and,

(C) said third portion is adapted to be deformed into the recess of a stake received in said socket to maintain said strip in substantially fixed orientation relative to said stake.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Fnberg 94-17 Fmk 9417 Jacobson 94-17 Carpenter 29509 Wilbur 9417 Black 24274 Pilskar 29-509 Wolff 24274 Artigl ass 'et a1. 9417 Tinsley 24274 Gaetke 94-51 I. SPENCER OVERHOLSER, Primary Examiner. G. A. KAP, R. S. ANNEAR, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,288,042 November 29, 1966 George 0. Gaetke It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 71, for "eolngated" read elongated line 73, for "end" read and column 4, line 3, for "mmebers" read members line 53, for "extendign" read extending Signed and sealed this 24th day of October 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

2. A CONCRETE FORM OF THE TYPE USED IN FORMING A KEY CONTRACTION JOINT BETWEEN ADJACENT CONCRETE SLABS, COMPRISING IN COMBINATION: (A) A PLURALITY OF STAKES ADAPTED TO BE VERTICALLY SET IN TRANSVERSELY ALIGNED RELATIONSHIP WITH THE UPPER ENDS THEREOF DISPOSED UNIFORMLY BELOW GRADE LEVEL; AND, (B) AN ELONGATED STRIP ADAPTED TO THE SUPPORT ON SAID STAKES, SAID STRIP HAVING: (1) LONGITUDINAL UPPER AND LOWER SUBSTANTIALLY COPLANER MEMBER ADAPTED TO ABUT AGAINST SAID STAKES UPON BEING SUPPORTED THEREON; (2) A LONGITUDINAL KEY DEFORMATION MEMBER INTERPOSED BETWEEN AND CONNECTED TO THE UPPER AND LOWER COPLANAR MEMBERS; AND, (3) AN INVERTED SOCKET FORMED ON THE UPPER COPLANAR MEMBER AND ADAPTED TO BE RECEIVED OVER SAID STAKES TO SUPPORT SAID STRIP THEREON, SAID SOCKET COMPRISING: (A) A FIRST PORTION EXTENDING LONGITUDIANLLY OF AND LATERALLY FROM THE UPPER EDGE OF THE UPPER OF SAID COPLANAR MEMBERS; (B) A SECOND PORTION EXTENDING LONGITUDINALLY OF SAID SUBSTANTIALLY VERTICALLY FROM SAID FIRST PORTION TO DEFINE A THIN SECTION; AND, (C) A THIRD PORTION EXTENDING FROM AND LONGITUDINALLY OF SAID SECOND PORTION IN SPACED RELATIONSHIP TO THE UPPER EDGE THEREOF AND IN SPACED SUBSTANTIALLY OPPOSED RELATIONSHIP TO THE UPPER OF SAID COPLANAR MEMBERS. 